There are various devices to measure heart rates. For example, one approach depends on wrapping a band across a person's chest. Electrodes in the band can sense the person's heart beat and wirelessly transmit the measured signals to a receiver. This approach can be quite inconvenient because the person has to wear a band across his chest in order to get the necessary measurements.
Another approach to measure heart beat is to clip an infrared sensor onto a person's finger. The sensor is connected to a machine through a wire. This approach is unsatisfactory if one intends to remain active, or to use one's hands while measurements are taken.
It should be apparent from the foregoing that there is still a need for an accurate heart rate monitor that is convenient to use for a person who may be in motion.